Planar Light Emitting Device FPC Overlap Connection
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Solution Overview
Problem
Conventional planar light emitting devices face challenges in achieving uniform in-plane luminance distribution due to high resistance in light-transmissive anode thin-film electrode layers, leading to uneven voltage and luminance, and existing FPC structures are costly and difficult to manufacture with precise connections.
Innovation Solution
A planar light emitting device with a plurality of flexible printed circuits (FPCs) on the back surface, where overlapping conductive layers establish electrical connections between adjacent FPCs, improving material utilization efficiency and simplifying wiring to the pads, and using a combination of L-shaped and I-shaped FPCs to form a square-annular shape for even light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light-transmissive anode thin-film electrode layer is used, then light emission is enabled, but high resistance causes uneven voltage distribution and luminance
Solution Approach 1:
The anode pad is divided into multiple segments (first anode pad and second anode pad) positioned at different locations. This segmentation allows current to be supplied from multiple points, reducing the resistance effect and achieving more uniform voltage and luminance distribution across the light-emitting surface.
2Reliability
If conventional FPC structures with jumper wires are used, then electrical connections are established, but manufacturing cost increases and production difficulty rises
Solution Approach 1:
The FPC connecting pads are directly bonded to each other through overlapping conductive layers, merging the connection function into the FPC structure itself. This eliminates the need for separate jumper wires and their associated soldering processes, reducing manufacturing steps and costs while maintaining reliable electrical connections.
Solution Approach 2:
The overlapping conductive layers on the FPC serve as an intermediary mechanism for electrical connection between adjacent FPCs. This direct bonding interface replaces the traditional jumper wire intermediary, simplifying the overall connection system.
3Reliability
If precise jumper wire soldering is required, then electrical connections are achieved, but productivity decreases and manufacturing precision requirements increase
Solution Approach 1:
The FPC structure is designed to self-connect through direct bonding of overlapping conductive layers. The conductive patterns on adjacent FPCs automatically form electrical connections when bonded together, eliminating the need for manual soldering operations and significantly improving productivity.
4Manufacturing precision
If multiple FPCs are used to supply power to multiple pads, then uniform luminance is achieved, but FPC structure complexity and material usage increase
Solution Approach 1:
Each FPC is designed with both anode-dedicated and cathode-dedicated equipotential regions, allowing a single FPC to serve multiple functions. The FPCs can be arranged in different configurations (L-shaped, I-shaped, rectangular) while maintaining the same basic structure, reducing overall system complexity.
Data Source
Figure 1A~1C
Figure 2~3
Figure 4~5
AI summary
The present invention provides a planar light emitting device which is highly productive employing inexpensive FPCs capable of being easily electrically connected, and which has a light emitting region with reduced unevenness in luminance and hence is highly reliable. A planar light emitting device, which has two main surfaces of a light emitting surface and a back surface, includes a planar light emitting tile including a planar light emitting element and a plurality of flexible printed circuits (FPCs) disposed on the back surface. Here, the planar light emitting tile includes a non-pad region where none of an anode pad and a cathode pad are disposed. Further, in an overlapped region where part of one circuit board and part of another circuit board overlap each other, an electrical connection site where an equipotential region of the one circuit board and that of the other circuit board are directly electrically connected to each other is formed. The non-pad region forms a connecting-part disposed region that overlaps with the electrical connection site.